Factors affecting hard-of-hearing (HOH) listeners' use of formant transitions in speech will be investigated in three experiments. Listeners will be selected on the basis of: 1) hearing loss: (a) mild-to- moderate or (b) moderate-to-severe, 2) audiometric configuration: (a) flat or (b) sloping, and 3) amount of auditory experience: (a) extensive, or (b) limited, as define by age of hearing loss onset, years of amplification use, and home/school mode of communication. The three experiments will use different approaches for the study of formant transition use by HOH listeners. These are: 1) investigation of listeners' use of formant transitions for glide and voiced stop consonant identification as a function of hearing loss and auditory experience. Spoken stimuli will be modified so that formant transitions are the only available acoustic cues for consonant identification. Transition audibility will be determined based on threshold measurements for each of the transition onset and offset frequencies. An audibility metric will be developed and applied to describe the effects of transition audibility on transition use. The relationships between use of formant transitions and the listeners' auditory experience will also be examined. 2) comparison of listeners' frequency/temporal discrimination for transition-like stimuli with transition use for consonant identification. The transition-like stimuli will simulate the transition characteristics found in the glide/stop identification stimuli. Relationships between transition discrimination and transition use will be described. 3) investigation of HOH listeners' perceptual weighting of formant transitions compared to other acoustic cues to the stop/glide contrast. Both synthesized and natural speech stimuli will be developed that vary along two acoustic continua (formant transition and amplitude onset). Analysis of the perceptual importance of the two acoustic cues, auditory experience, and degree of hearing loss will be completed. In all experiments, listeners with normal hearing thresholds will be used as controls.